Based upon a wide range of historical and literary sources, An Apprenticeship in Arms is a scholarly study of the military experiences of peers and gentlemen from the British Isles who volunteered to fight in the religious and dynastic wars of mainland Europe, as well as the ordinary men who were impressed to serve in the ranks from the time of the English intervention in the Dutch war of independence in 1585 to the death of the soldier-king William III in 1702. This apprenticeship in arms exposed these men to the technological innovations of the military revolution, laid the foundations for a fledgling professional officer class based upon merit and established a fund of military expertise. This remilitarization of aristocratic culture and society was completed by 1640, and provided numerous experienced military officers for the various armies of the civil wars and, subsequently, for the embryonic British army after William III invaded and conquered the British Isles and committed the Three Kingdoms to the armed struggle against Louis XIV during the Nine Years War.

Conflicts between amateur aristocrats and so-called 'soldiers of fortune' led to continuing debates about the relative merits of standing armies and a select militia; the individual pursuit of honour and glory by such amateurs also obscured the more rational military and political objectives of the modern state, subverted military discipline, and delayed the process of the professionalization of the officer corps of the British army.